For tissue repair or regeneration, cells must migrate into a wound bed, proliferate, express matrix components or form extracellular matrix, and form a final tissue shape. Multiple cell populations must often participate in this morphogenetic response, frequently including vascular and nerve cells. Matrices have been demonstrated to greatly enhance, and in some cases have been found to be essential, for this to occur. Natural cell in-growth matrices are subject to remodeling by cellular influences, all based on proteolysis, e.g., by plasmin (degrading fibrin) and matrix metalloproteinases (degrading collagen, elastin, etc.). Such degradation is highly localized, and only upon direct contact with the cell. In addition, the delivery of specific cell signaling proteins, such as growth factors, is tightly regulated.
When a tissue is injured, polypeptide growth factors which exhibit an array of biological activities are released into the wound where they play a crucial role in healing (see, e.g., Hormonal Proteins and Peptides, Li, C. H., ed., Volume 7, Academic Press, Inc. New York, pp. 231-277 and Brunt et al., Biotechnology 6:25-30 (1988)). These activities include, recruiting cells, such as leukocytes and fibroblasts, into the injured area, and inducing cell proliferation and differentiation. Growth factors that participate in wound healing include: platelet-derived growth factor (PDGF), insulin-binding growth factor-1 (IGF-1), insulin-binding growth factor-2 (IGF-2), epidermal growth factor (EGF), transforming growth factors (TGF-α), transforming growth factor-β (TGF-β), platelet factor 4 (PF-4), and heparin binding growth factors one and two (HBGF-1 and HBGF-2).
Fibrin is a natural material which has been reported for several biomedical applications. Fibrin gels have been used as sealants due to their ability to adhere to many tissues and their natural role in wound healing. Some specific applications include use as a sealant for vascular graft attachment, heart valve attachment, bone positioning in fractures and tendon repair. Additionally, these gels have been used as drug delivery devices, and for neuronal regeneration as well as material for cell in-growth matrices (U.S. Pat. No. 6,331,422 to Hubbell et al.).
The incorporation of bioactive factors in natural or synthetic biomaterials or mixtures thereof are mainly done by incorporation of the bioactive factor through physical interaction as has been described, for example, in U.S. Pat. Nos. 6,117,425 and 6,197,325 and WO02/085422. Covalent linking of the bioactive factor to the biomaterial is a more advanced technique allowing improved control of the release profile of the bioactive factor from the biomaterial. The incorporation of small synthetic or naturally occurring molecules, peptides and/or proteins into fibrin matrices through action of transglutaminases has been described in U.S. Pat. Nos. 6,331,422; 6,468,731 and 6,960,452 and WO 03/052091 and Schense, J. C., et al. (1999) Bioconj. Chem. 10:75-81. Covalent cross-linking of the bioactive factor may be performed by modifying the bioactive factor through incorporation of functional groups, which are able to react with one or more of the reactive groups of the precursor components or biomaterials during or after formation of the biomaterial. U.S. patent application No 2003/0187232 discloses a fibrin gel supplemented with a PDGF modified with transglutaminase substrate domain and its use in chronic wound healing in human patients. However, with the system describes therein, a high amount of growth factor is released from the fibrin gel in the first hours after application.
While delivery systems for proteins and growth factors are known, there remains a need for controlling the amount of growth factor released over time as well as the rate of release of the growth factor. In particular, there is a need to reduce the amount of growth factor to be released in the first hours following application
It is therefore an object of the present invention to provide fibrin matrices for enhanced controlled and/or sustained release of growth factors.
It is a further object of the present invention to provide methods for the formation of a fibrin matrix supplemented by growth factors.
It is a further object of the present invention to provide compositions and methods for the formation of a fibrin foam supplemented with growth factors.
It is a further object of the present invention to provide methods for the formation of a fibrin foam supplemented by growth factors.